There has been a continuing need for improved methods for the preparation of mineral compositions, especially phosphorus-containing minerals. This long-felt need is reflected in part by the great amount of research found in the pertinent literature. While such interest and need stems from a number of industrial interests, the desire to provide materials which closely mimic mammalian bone for use in repair and replacement of such bone has been a major motivating force. Such minerals are principally calcium phosphate apatites as found in teeth and bones. For example, type-B carbonated hydroxyapatite [Ca5(PO4)3-x(CO3)x(OH)] is the principal mineral phase found in the body, with variations in protein and organic content determining the ultimate composition, crystal size, morphology, and structure of the body portions formed therefrom.
Calcium phosphate ceramics have been fabricated and implanted in mammals heretofore in many different forms including as shaped bodies, in cements and otherwise. Different stoichiometric compositions such as hydroxyapatite (HAp), tricalcium phosphate (TCP), and tetracalcium phosphate (TTCP), have all been employed to this end in an attempt to match the adaptability, biocompatibility, structure and strength of natural bone. Despite tremendous efforts directed to the preparation of improved calcium phosphate and precursor hydroxyapatite materials for such uses, significant shortcomings still remain.
Early ceramic biomaterials exhibited problems derived from chemical and processing shortcomings that limited stoichiometric control, crystal morphology, surface properties, and, ultimately, reactivity in the body. Intensive milling and comminution of natural minerals of varying composition was required, followed by powder blending and ceramic processing at high temperatures to synthesize new phases for use in vivo.
A number of patents have issued which relate to ceramic biomaterials. Among these are U.S. Pat. No. 4,880,610, B. R. Constantz ,“In situ calcium phosphate minerals-method and composition;” U.S. Pat. No. 5,047,031, B. R. Constantz, “In situ calcium phosphate minerals method;” U.S. Pat. No. 5,129,905, B. R. Constantz, “Method for in situ prepared calcium phosphate minerals;” U.S. Pat. No. 4,149,893, H. Aoki, et al, “Orthopaedic and dental implant ceramic composition and process for preparing same;” U.S. Pat. No. 4,612,053, W. E. Brown, et al, “Combinations of sparingly soluble calcium phosphates in slurries and pastes as mineralizers and cements;” U.S. Pat. No. 4,673,355 E. T. Farris, et al, “Solid calcium phosphate materials;” U.S. Pat. No. 4,849,193, J. W. Palmer, et al., “Process of preparing hydroxyapatite;” U.S. Pat. No. 4,897,250, M. Sumita, “Process for producing calcium phosphate;” U.S. Pat. No. 5,322,675, Y. Hakamatsuka, “Method of preparing calcium phosphate;” U.S. Pat. No. 5,338,356, M. Hirano, et al “Calcium phosphate granular cement and method for producing same;” U.S. Pat. No. 5,427,754, F. Nagata, et al.,“Method for production of platelike hydroxyapatite;” U.S. Pat. No. 5,496,399, I. C. Ison, et al., “Storage stable calcium phosphate cements;” U.S. Pat. No. 5,522,893, L. C. Chow. et al., “Calcium phosphate hydroxyapatite precursor and methods for making and using same;” U.S. Pat. No. 5,545,254, L. C. Chow, et al., “Calcium phosphate hydroxyapatite precursor and methods for making and using same;” U.S. Pat. No. 3,679,360, B. Rubin, et al., “Process for the preparation of brushite crystals;” U.S. Pat. No. 5,525,148, L. C. Chow, et al., “Self-setting calcium phosphate cements and methods for preparing and using them;” U.S. Pat. No. 5,034,352, J. Vit, et al., “Calcium phosphate materials;” and U.S. Pat. No. 5,409,982, A. Imura, et al “Tetracalcium phosphate-based materials and process for their preparation.”
While improvements have been made in ceramic processing technology leading to ceramic biomaterials with better control over starting materials and, ultimately, the final products, improved preparative methods are still greatly desired. Additionally, methods leading to calcium phosphate containing biomaterials which exhibit improved biological properties are also greatly desired despite the great efforts of others to achieve such improvements.
Accordingly, it is a principal object of the present invention to provide improved minerals, especially phosphorus-containing minerals.
A further object of the invention is to provide methods for forming such minerals with improved yields, lower processing temperatures, greater flexibility and control of product formation, and the ability to give rise to minerals having improved uniformity, biological activity, and other properties.
Another object is to improve the yield and control of synthetic mineral formation processes.
Yet another object is to give rise to cement compositions useful in the repair or replacement of bone in orthopaedic and dental procedures.
A further object is to provide minerals which are both substantially uniform and which are non-stoichiometric.
Further objects will become apparent from a review of the present specification.